1. Field of the Invention
The present invention relates to a combustion device which is made up of a plurality of tubular burners disposed side by side with one another. Each of the tubular burners includes: a mixing tube with an inlet port at a rear end thereof into which inlet port air-gas mixture of a fuel gas and primary air flows; and a flame hole member which has a plurality of flame holes and which is adapted to be fitted into a front end portion of the mixing tube such that the air-gas mixture is ejected forward through the flame holes so as to perform combustion.
2. Description of the Related Art
As this kind of combustion device, there is conventionally known one which is described in U.S. Pat. No. 5,186,620. In this conventional combustion device, a plurality of mixing tubes of a plurality of tubular burners disposed in parallel (or side by side) with one another are manufactured by combining together two plate members having formed therein a plurality of half-split shape of mixing tubes at a distance from one another. Accordingly, a clearance is formed between front end portions of the two plate members so as to communicate a mixing tube with an adjoining mixing tube. The above-mentioned clearance constitutes a carryover flame hole which is rectangle in shape and through which the air-gas mixture is ejected forward.
By the way, in such a portion of the carryover flame hole as is close to each of the mixing tubes, the air-gas mixture from each of the mixing tubes will be ejected sufficiently. However, in an intermediate portion of the carryover flame hole as seen in a lengthwise direction of the carryover flame hole (in a direction in which the tubular burners are disposed in a side-by-side relationship), the air-gas mixture from each of the mixing tubes becomes hardly ejected, thereby deteriorating the carryover performance. As a solution, in the above-mentioned conventional example, in an intermediate portion as seen in the lengthwise direction of the carryover flame hole, there is provided an intermediate flame hole which recedes further backward from the front end of the remaining portions of the carryover flame hole.
In the above-mentioned conventional example, the front end of each of the plate members is provided with a notched portion which recedes backward, thereby constituting an intermediate flame hole. As a result, the air-gas mixture becomes easier to be ejected out of the intermediate flame hole. However, not only is the air-gas mixture ejected forward out of the intermediate flame hole, but also is the air-gas mixture diffused in a direction of the normal to the plate member through the notched portions. As a result, the amount of such ejected gas in the forward direction as is required for the carrying over of the flame decreases, whereby sufficient carrying over performance cannot be obtained.